The effect of hydrochar particle size on the physical and hydraulic properties of sandy loam soil

Document Type : Research Paper

Authors

• Reza Allahi Ashlooblagh ¹
• Hamid zareabayneh ²
• Atefeh Azadifar ³

¹ Master student, Department of Water Science, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran.

² Professor, Department of Water Science, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran.

³ PhD student, Department of Water Science, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran.

Abstract

Keywords

• Available water
• particle size
• bulk density
• saturated hydraulic conductivity
• hydrochar

Main Subjects

• آبیاری و زهکشی

Introduction:

A significant portion of Iran is characterized by arid and semi-arid regions. To enhance soil fertility in these areas, the addition of organic matter is highly recommended. Organic matter decomposes rapidly within the soil, resulting in the release of carbon dioxide, water, and various other substances. The rising emissions of greenhouse gases, particularly carbon dioxide, into the atmosphere are driving global warming and climate change. Currently, the search for solutions to mitigate this phenomenon has garnered significant attention from scientists worldwide. The conversion of plant biomass into hydrochar is recommended as a strategy to prevent the increase in global warming and to enhance the physical, chemical, and hydraulic properties of soil.

Objective:

According to our knowledge, there has been no research conducted on the effect of particle size of hydrochar derived from sunflower stems on the physical and hydraulic characteristics of soil. Therefore, the objective of this study was to investigate the influence of the particle size of hydrochar from sunflower stems on some physical and hydraulic properties of soil under laboratory conditions.

Material and method:

This research was conducted in the drainage research laboratory at the faculty of agriculture, Bu-Ali-Sina university, Hamadan, in the year 2023. The study investigated various soil properties, including bulk density, porosity, saturated moisture content, field capacity, permanent wilting point, available water, discharge, velocity, hydraulic conductivity and pore-water velocity. To evaluate the physical and hydraulic characteristics of soil, a mixture of 3% by weight of three particle sizes (0-0.5 mm, 0.5-1 mm, and 1-2 mm) of sunflower stem hydrochar was combined with sandy loam soil. The hydrochar produced resulted from a hydrothermal process on sunflower stems at a temperature of 200 degrees Celsius for 20 hours under 18 bar pressure. PVC columns with a length of 30 cm and a diameter of 5.95 cm were utilized for the experiments. The volume of sunflower stalk hydrochar necessary to fill each column to a height of 10 cm was calculated and subsequently mixed with the soil separately. Then, to assess the effect of hydrochar on the soil, the soil columns were maintained for 120 days under field capacity conditions (FC = 0.23) in a laboratory environment. Irrigations were conducted every 4 days over a period of 120 days.

Result and Discussion:

The results indicated that the particle size of sunflower stem hydrochar had a significant effect at the 1% probability level on the physical, hydraulic, and moisture characteristics of the soil. The most influential factor on the measured parameters was the hydrochar with a particle size of 0-0.5 mm, which led to a 21.36% reduction in bulk density, and increases of 30.58%, 26.73%, 49.27%, 118.7%, and 34.10% in porosity, saturated moisture, field capacity moisture, permanent wilting point moisture, and available water, respectively, compared to the control soil. The variations in bulk density and porosity of soil treatments containing hydrochar can be attributed to the spherical morphology of the hydrochar structure and its deformability. The application of hydrochar with a 0-0.5 mm particle size also resulted in a 65.42% reduction in discharge, velocity, hydraulic conductivity, and a 73.65% reduction in pore velocity compared to the control soil. Hydrochar primarily influences hydraulic conductivity by modifying the macropores within the amended soil. Analysis of the moisture characteristics curve indicated that hydrochar, regardless of particle size, increased mesopore and micropore, consequently enhancing soil water retention across various suction levels, especially at suctions ranging from 0 to 2000 cm. The water retention curve in soil is influenced by various factors, including organic matter content, soil porosity, and bulk density. The application of hydrochar with a fine particle size led to the development of microspore, thereby enhancing water retention.

Author Contributions

1. Allahy Ashloblagh: Investigation, Methodology, Gathering and analysis of data, Writing and editing the manuscript. H. Zareabyaneh: Conceptualization, Investigation, Methodology, Supervision, Funding acquisition, Validation, Writing and editing the manuscript. A. Azadifar: Conceptualization, Investigation, Methodology, Supervision, Validation, Writing and editing the manuscript. The final text was reviewed and approved by all authors. The authors say they have no competing interests.

Data Availability Statement

Data is available on reasonable request from the authors.

Acknowledgements

The authors would like to thank the reviewers and editor for their critical comments that helped to improve the paper. The authors gratefully acknowledge the support and facilities provided by the Department of water Science, University of Bu-Ali Sina University, Iran.

Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Conflict of interest

The author declares no conflict of interest.